Rotary-type optical head

Abstract

An optical head which can be rotated about the rotation center by a magnetic force. There is a photodetector which is divided into a plurality of detection regions and as the optical head rotates, different detection regions are examined to determine a tracking error. Rotating between the inner and outer peripheral portions of an optical disk, the optical head selects a track on the optical disk on which information is recorded, radiates a light beam focused on the selected track, receives the light beam reflected by the optical disk to a second photodetector having three divided parallel sensor segments, and reproduces the information recorded on the optical disk. In consideration of the fact that in an optical disk rotated at a constant angular velocity, the degree of modulation of a retrieving information signal recorded on a recording layer on the optical disk is increased toward the outer peripheral portion, the sensor segments of the photodetector are arranged such that the projection of a track on the inner peripheral portion in an information recording area, of track projections which move on the sensor segments, does not cross the three divided sensor segments upon rotation of the optical head.

What is claimed is: 
     
       1. An optical head comprising: a rotating member arranged to be rotatable in a direction to cross tracks formed on an optical disk;   means for radiating and focusing a light beam on the optical disk;   a photodector for detecting a tracking error signal representing a tracking error of the light beam with respect to the optical disk; and   means for guiding light reflected by the optical disk into said photodetector,   wherein regions where beam spots of "0th-order light" and "diffracted light" of the reflected light on said photodetector overlap in accordance with rotation of said rotating member are used as detection regions for detecting the tracking error signal.   
     
     
       2. An optical head according to claim 1, wherein said photodetector is arranged behind a reflecting mirror for transmitting a half of the reflected light of the focused light beam and reflecting a remaining half of the light at a predetermined angle. 
     
     
       3. An optical head according to claim 1, wherein said rotating member is arranged in a direction perpendicular to a center line extending through said radiating means and a rotation center of said rotating member, rotated about the rotation center and moves between an inner track and an outer track in the recordable area on the optical disk, and arranged to be freely rotated within a range of 30° in right and left directions of the optical disk, respectively, with respect to the center line perpendicular to a center track in the information recording area. 
     
     
       4. An optical head comprising: a rotating member arranged to be rotatable in a direction to cross tracks formed on an optical disk;   means for radiating and focusing an incident light beam on the optical disk which is reflected off of the optical disk;   a photodetector   means for guiding the light reflected off of the optical disk onto said photodector;   said photodetector having a plurality of detection regions for detecting overlapping of "0th-order light" and "diffracted light" of the reflected light as said rotating member rotates, each detecting region having an output for generating a detection signal;   an operation circuit having inputs; and   a switching means selectively connecting the outputs of the detection regions of said photodetector to the inputs of the operation circuit;   said operation circuit for generating a tracking error signal by determining a difference between detection signals output by outputs of said detection regions which are selectively connected to said operation circuit by said switching means.   
     
     
       5. An optical head according to claim 4, wherein the plurality of detection regions are obtained by radially dividing a detection region of said photodetector from a center thereof.